1. Field of the Invention
This invention relates to improvements in ophthalmology and more particularly to improvements in artificial intraocular lenses (pseudophakoi) used for correction of aphakia and reestablishment of binocularity in aphakia.
2. Discussion of the Prior Art
Well-fixed and well-centered intraocular lens implants are known to produce stable retinal images with stable space localization and offer the best chance of re-establishment of binocularity in cases of aphakia.
Many techniques of lens implantation, including suturing to the ciliary muscle as disclosed in U.S. Pat. No. 3,711,870 and iris diaphragm fixation as disclosed in U.S. Pat. No. 3,673,616 have been used. The latter is considered to be a safe procedure giving good stability and the present invention deals with improvements in this general type of pseudophakos. More particularly, the invention relates to improvements in "iridocapsular" and/or "iris clipped" implants which have haptic sections respectively comprised of posterior and both posterior and anterior fastening elements all of which will be referred to as iris clips. The iris clips may be in the form of loops and/or struts of filament fastened to and extending away from the lenses.
Heretofore, iris clips have been formed of biologically inert metal wires which are at least in some respects, less than optimum in purpose. Even when formed of least dense of useful metals or alloys such loops and/or struts are relatively heavy in the eye, opaque and unaesthetic, less than optimally manipulatable before and/or during the surgical implantation and expensive both from the standpoint of precious metal cost and the intricacy of looped manufactured, not to mention the wire manufacturing operation itself.
An alternative to the use of metals for iris clips is that of using plastics, i.e. transparent or translucent filament or fiber formed of nylon, polymethyl methacrylate, polypropylene or other similarly chemically pure and biologically inert materials known to be available in the art. Fastening of these usually difficult to handle thin sections of plastics, however, has presented serious manufacturing problems. Staking, press fitting or interference fitting and other such attempts to fasten plastic iris cips in place are inherently difficult and tedious operations attended by high scrap yield and usually less than complete assurance against loosening or disconnection of parts during or following surgical implantation.
The use of adhesive which may avoid some of the problems of mechanical fixation procedures is, on the other hand, often turned away from for reasons of the possibilities of dangerous loosening and/or disasterous detachment of parts in the eye as a result of attack upon the bond or adhesive itself by ocular fluids.
It has been proposed in copending application Ser. No. 779,384, filed Mar. 21, 1977 that rigid ferruling be swaged, crimped or heat-sealed to ends of plastic iris clips and in turn anchored in apertured lenses by cold flow of the lens material around the ferruling.
While many of the drawbacks of older means and methods of anchoring iris clips are overcome by the invention of application Ser. No. 779,384, a disadvantage thereof is the difficulty of fitting a rigid ferrule having a blind hole onto an end of flexible iris clip material or vice versa. Another disadvantage is the tendency of plastic iris clip filament to experience stress release with time so that a squeeze fit at time of ferruling may not remain secure after stress release has occurred. Also, the close tolerence heretofore needed between diameter of filament and hole size in the ferrule render fabrication difficult, time consuming and costly.
In view of the foregoing, it is a principal object of this invention to overcome present difficulties and drawbacks attending the fixing of iris clips to lenses of pseudophakoi and more particularly to overcome the problems and difficulties currently experienced in providing these lenses with iris clips formed of plastic filaments.
A more specific object of the invention is to provide a novel and improved system and method for fixing plastic iris clips to lenses of pseudophakoi wherewith the attachment can be made simply, efficiently and economically especially with and added assurance of permanence throughout the expected useful life of the product.
Another object is to improve the locking of rigid ferruling to a less rigid iris clip filament while preserving the well known advantages of posterior blind hold anchoring which affords smooth and uninterrupted anterior lens surfaces.
Still another object is to provide for ease of fabrication and relaxation of dimensional tolerences in the ferruling of intraocular lens clips and to accomplish greater reproducibility of tight ferruling with minimal stress and avoidance of opportunity for subsequent stress corrosion.
Other objects and advantages of the invention will become apparent from the following description.